In vertebrate animals, retinal neural circuits process images, extracting information about color, shape size and movement from visual surroundings. While laboratory animals such as cat, rat, mouse and rabbit provide plausible models of human nocturnal vision, zebrafish, like humans and other old-world primates, are remarkable for diurnal color vision. Zebrafish is a tetrachromat with 4 cone photoreceptor types selectively sensitive to red, green, blue and ultraviolet wavelengths. Studies of the neural circuitry through which this rich color information is processed can be aided through studies of fish lines with additional special-purpose genes. In these transgenic fish, selected neural types in retina can be visualized in the fluorescent microscope, so that these cells can be easily recognized. These special transgenic lines are developed and used in experimental studies of the retina, where they aid in the ability to determine circuitry connections for image processing among retinal neurons. The zebrafish lines generated and maintained under this protocol were created in other laboratories, where extra genes were added to, or deleted from, the DNA. In some cases new phenotypes are created in house by cross breeding. Adult fish produced in this research program will be studied according to goals and objectives described in another research program (NS002631-30). This describes the use of microelectrodes both to record electrical signals from retinal neurons, and to label them with fluorescent dyes. The combined markers consisting of genetic and microelectrode labels will aid in discerning circuitry connections among retinal neurons, and provide more information about the neural pathways through which images are processed.